Identical puncturing of UE identification data and load data in the HS-SCCH channel

ABSTRACT

The present invention relates to a method for transmitting data via a physical channel in a communication system, the channel being used by at least one first communication device and one second communication device and transmitting data with a defined bit rate. According to the present invention, the data to be transmitted (TD) is composed of load data (LD) and identification data (ID) for identifying the second communication device, the load data (LD) and identification data (ID) are coded separately from one another, the respective coding (C_LD, C_ID) takes place in such a way that an identical bit rate is achieved after the coding operation for the load data (LD) and the identification data (ID) and the rate is matched to the bit rate that has been defined for the physical channel by a rate matching mode, which defines which bits are punctured or repeated in a data stream. The rate matching model for load data (LD) and identification data (ID) is identical.

BACKGROUND OF THE INVENTION

The present invention relates to a method for transmitting data whereinthe transmission bit rate is defined via the physical channel.

Owing, for example, to their being embedded in specific transmissionformats, transmission channels in mobile radio systems only offer fixeddata or, as the case may be, raw data transmission rates, while the datarates of different signals or applications differ therefrom. Such datarates consequently need to be mutually matched at an interface.

Matching of such type is described below using an example taken from theUMTS standard:

In the UMTS (Universal Mobile Telecommunication System), data packetsare sent to a mobile station (UE=User Equipment) on the high-speeddownlink shared channel (HS-DSCH). The associated control information,such as the channelizing codes used for the HS-DSCH and the modulationscheme, such as QPSK (Quadrature Phase Shift Keying) or 16QAM (16Quadrature Amplitude Modulation), is sent on the high-speed sharedcontrol channel (HSSCCH). Such control information or, as the case maybe, this load data is linked to identification information so that thereceiving mobile station can recognize that the information on theHS-SCCH is intended for it. “Masking of the data” is a term also used inthis connection. Prior to linking, both load data and identificationdata undergo coding and, in each case, immediately ensuing ratematching.

This process is highly complex, however, which is disadvantageousparticularly where the mobile radio device is concerned inasmuch as suchcoding and rate matching processes are cancelled again in order toarrive at the original (load) data.

Proceeding from this prior art, the present invention seeks to carry outrate matching in a less complex manner in one channel used jointly by anumber of communication participants.

SUMMARY OF THE INVENTION

The present invention centers on organizing rate matching for load dataand identification data, serving to indicate for what device the data isintended, according to a common scheme, with overall coding beingeffected in one channel used jointly by a number of communicationparticipants. As such, decoding, in particular on the recipient's side,is made less complex. A further feature of the present invention isaimed at providing a rate matching pattern that permits rate matching inaccordance with a common scheme while retaining the original informationas faithfully as possible.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an overview of overall coding in a channel where the databeing transmitted is masked with the aid of the identification data.

FIG. 2 is a scheme showing the individual operations involved in overallcoding.

FIG. 3 shows the manner in which overall coding has been achievedhitherto in the HS-SCCH according to the prior art.

FIG. 4 is an exemplary embodiment of the present invention of overallcoding in the HS-SCCH.

FIG. 5 shows an exemplary implementation on the recipient's side forreceiving the HS-SCCH in the case of the specification currentlyemployed (Release 99).

FIG. 6 is an exemplary embodiment of the implementation on therecipient's side in the case of overall coding according to the proposalshown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Overall Coding of Load and Identification Data

FIG. 1 is a schematic of overall coding for load data (LD: Load Data)and identification data (ID: Identification Data) sent on a jointly usedchannel in a communication system. Transferred data (TD: TransferredData) here consists of load data (LD) that is linked to theidentification data ID in order to make it apparent for which recipientthe transferred data TD is intended. Load data LD and identificationdata ID is linked as part of overall coding, in most cases channelcoding (CC: Channel Coding). Channel coding is understood as referringto the matching of digital values to the physical transmission medium,referring to, for instance, coding followed immediately by ratematching. Overall coding refers in this case to the coding, ratematching, and linking of the load and identification data. It is not,however, absolutely essential for all the listed steps to be carriedout. Overall coding also can, for instance, include coding alone with norate matching.

Although the scheme shown in FIG. 1 is known per se, the prior art andthe present invention differ with respect to the procedure employed foroverall coding.

Individual procedural blocks within overall coding CC are shown brokendown in FIG. 2. The load data LD is first subjected to coding C_LD.Redundancy is added to the load data LD in the course of such coding,for which, in particular, convolutional codes are used, as a result ofwhich the sent data TD can be recovered more reliably on the recipient'sside. The code respectively employed for coding is characterized by itscode rate R=K/N, where K is the number of data bits or message bits tobe transmitted and N is the number of bits present after coding. As arule, the efficiency of the code is greater the lower the code rate.However, a problem associated with the coding is that the data rate isreduced by the factor R. In order to match the data rate of the codeddata stream to the respectively possible transmission rate, ratematching RM_LD is performed in the transmitter whereby, in keeping witha specific pattern, bits are either removed from or repeated in the datastream. The removal of bits is referred to as “puncturing” and theirrepetition is referred to as “repeating”.

The identification data ID is analogously first subjected to coding C_IDand then to rate matching RM_ID. The identification data and load dataare then linked to each other in a linking operation L, through whichthe data TD being transferred is formed.

Although the procedure shown in FIG. 2 is known in terms of itsprinciple, the prior art and the present invention differ in the wayrate matching is implemented for the load data LD and identificationdata ID.

FIG. 3 illustrates the implementation of overall coding of HS-SCCH Part1 according to the current UMTS standard specification (FDD, Release 5).The load data LD is here formed by the channel information bitsx_(ccs,1), x_(ccs,2), . . . x_(ccs,7). The channel information bits arereferred to in specialist technical circles as “channelization code setbits”. Modulation scheme bit x_(ms,1) also flows into the load data.Such load data is encoded via a rate 1/3 convolutional encoder accordingto the standard established in 1999 (Release 99). Eight tail bitsappended to the end of the bit block prior to coding enable simpler andmore reliable decoding on the recipient's side. The multiplexer MUXenables channel information bits X_(ccs) and the modulation scheme bitX_(ms) to be interrogated in an alternating manner. The totality of datapresent after the multiplexer's operations is referred to as X₁.

16 bits are thus present at the input side of the coder or encoder or,as the case may be, prior to the coding operation C_LD, whereas 48 bitsare present at the output side of the encoder Encod or, as the case maybe, after the coding operation C_LD, owing to the rate 1/3. Let thiscoded bit block be designated Z₁. The index 1 signifies that it is aquantity concerning Part 1 of the HS-SCCH. Part 1 of this controlchannel contains data which the recipient must decode immediately inorder to process incoming data on the HS-DSCH (HS-DSCH=HS DownlinkShared Channel) accordingly. The presence of the data of part 2 iscorrespondingly less time-critical.

However, only 40 bits are available on the physical channel, which is tosay the actual transmission channel, for transmission for Part 1 of thecontrol channel HS-SCCH. In order to arrive from 48 bits to the 40 bitswhich can be physically transmitted in Part 1, rate matching isperformed according to the following rate matching pattern (pattern 1):From the bit block or the sequence Z₁ proceeding from the codingoperation C_LD, the bits are punctured at positions 1, 2, 4, 8, 42, 45,47, 48. If use is made of a notation with a second index j, whichidentifies the bit position and, in the case shown, runs from 1 to 48,then the bits being punctured can be specified as Z_(1,1), Z_(1,2),Z_(1,4), Z_(1,8), Z_(1,42), Z_(1,45), Z_(1,47), Z_(1,48). The firstindex indicates as previously that it is Part 1 of the HS-SCCH. In thisnotation, the sequence R_(1,1), R_(1,2), . . . R_(1,40) will then bepresent in FIG. 3 after the rate matching operation.

The control channel HS-SCCH is monitored by a number of mobile stationsor mobile radio devices (UE: User Equipment). To identify therespectively addressed mobile station UE or, as the case may be, so thatsuch mobile station can decode Part 1, and also so that a mobile stationwhich is not addressed will recognize this fact, the load data,consisting of channel information data and of the modulation scheme, isidentified via the identification data or, as the case may be, via aspecific mask dependent on the mobile station's identification number.In the case illustrated here, what is termed a scrambling code (mask)specific to the mobile station's identification number is generated onthe mobile station's 16-bit identification number (UE ID) via rate 1/2coding according to the standard established in 1999 (Release 99).

The mobile station's identification number UE ID is assigned to themobile station in the relevant cell by the respective base station.

Scrambling is understood as “personalizing” of the information. This isdone via what are termed “scrambling codes”, by which the signal ismodified in order to separate or to split signals intended forindividual terminals or base stations from each other.

To generate the scrambling code, the 16 bits of the mobile station'sidentification number UE ID X_(ue,1), . . . X_(ue,16) and the appendedeight tail bits are coded according to the 1999 standard (Release 99)via the rate 1/2 convolutional coder (C_ID). (16+8)×2=48 bits of asequence B are then also present at the output of the convolutionalcoder. In order to arrive here at the length of 40 bits, for ratematching RM_ID the rate matching algorithm taken from the 1999 standard(Release 99) is used for puncturing (RM_ID), during which operation bitsb₁, b₇, b₁₃, b₁₉, b₂₅, b₃₁, b₃₇, b₄₃ in the sequence B, consisting ofbits b₁, b₂, . . . b₄₈, where the index indicates the bit position, arepunctured. The necessary reduction from 48 to 40 bits is produced withthe sequence C, consisting of bits c₁, c₂, . . . c₄₀, formed in thisway.

Different rate matching patterns are therefore used for the branch ofthe load data LD and the branch of the identification data ID for ratematching, RM_LD and RM_ID respectively, of such data. The reasons forthis are as follows:

-   -   The number of bits present in the branch with the identification        data ID or, as the case may be, in the branch with the load data        LD is generally not the same after the coding stage. The cause        of this may lie both in the number of output bits, which is to        say in the number of bits in the mobile station's identification        number or, as the case may be, channel information bits or        modulation information bits, and in the rate of coding.        Different rate matching will then be necessary.    -   Coding in the coding stage C_(LD) or, as the case may be, C_(ID)        serves inter alia to interlace the bits so that the original bit        sequence X_(i) or, as the case may be, X_(UE) can be restored on        the recipient's side even if transmission conditions are poor.        Interlacing that is good in these terms will, of course, appear        different for different input data X_(UE) or, as the case may        be, X_(i) (=X_(ccs) or X_(ms)), in particular also when        different coding rates are used. Individual bits consequently        have different significance after the coding stage. Such        different significance depends on the number of coding stage        input bits with which an output bit of the coding stage is        associated. The greater the number of input bits flowing into        the output bit, the more significant will be the output bit for        restoring the original data. In one rate matching pattern, when        data is punctured it is now preferable to puncture those bits        having in present terms lesser significance. In other words when        different coding is employed, such as with different        convolutional coders, followed by rate matching, different rate        matching patterns result in different distance properties in        terms of the Hamming distances of the resulting code sequences        or, as the case may be, codewords, and hence determine the        efficiency of the coding.

The use of different rate matching patterns and the computing andstorage requirements associated therewith pose only a minor problem inthe base station as suitable hardware is available there for managingeven highly complex computing processes. However, this does not apply tothe receiving mobile station.

As already mentioned, the present invention seeks to make overallcoding, rate matching in particular, less complex than it is at present,which is to say according to the specification according to Release 5.

A feature of the present invention is to perform rate matching foridentification data ID and load data LD according to a common ratematching pattern. Basically, two approaches to a solution areconceivable here:

-   i) Using a common rate matching pattern but performing rate matching    separately for load data LD and identification data ID.-   ii) Using a common rate matching pattern and performing rate    matching in common.

FIG. 4 shows a procedural flow embodied according to approach ii);likewise, for the example of the control channel HS-SCCH. In this case,the identification data ID, here designated identification bit sequenceX_(ue), and the channel information data, here X_(ccs) and X_(ms), arealready linked to each other according to the respective coding C_LD or,as the case may be, C_ID, then subjected to common rate matching. Suchlinking is performed via, for instance, an XOR function if the twovalues a bit can in each case assume are defined with 0 and 1. If thevalues −1 and 1 are assumed, linking can be performed via amultiplication operation. It is, however, also possible to use othertypes of bit-by-bit linking.

The data proceeding from the coding operation is designated, analogouslyto FIG. 3, Z₁ in FIG. 4. As a departure from FIG. 3, the bit block or,as the case may be, bit sequence or sequence R₁ here designates the dataprior to common rate matching but after linking.

The following advantages are achieved by a procedure according toapproach i) or ii):

As rate matching is only performed with one rate matching pattern,decoding in the recipient device, such as the mobile station UE, iscommensurately simpler. Reduced complexity is already achieved if ratematching is performed separately according to the same pattern foridentification data ID and load data LD (approach i).

If rate matching is combined according to approach ii), this will resultin further simplification.

Different Rate Matching Patterns

A further feature of the present invention is the provision of a ratematching pattern that is suitable as a common scheme approximatelyequally for load data LD and identification data ID. An aspect here,inter alia, is for the Hamming distance after linking to be as large aspossible; foir example, so that the linked data can be reconstructed asfaithfully as possible if transmission was faulty. A large Hammingdistance is desirable here also, in order, furthermore, to preserve theinformation content of the load data as well as possible. These andother criteria such as, for instance, the signal-to-noise ratio, are,however, not necessarily mutually independent, a fact that can result,inter alia, in the attempt to find an “optimized” rate matching patternleading to a number of different rate matching patterns which, expressedmathematically, also could be designated as secondary minima of theoptimizing problem. Among others, some variants have particularadvantages for the common rate matching pattern:

a) Use of the present puncturing algorithm (Release 99):

Bits r1,1, r1,7, r1,13, r1,19, r1,25, r1,31, r1,37, r1,43 are puncturedin the sequence r1,1, r1,2, . . . , r1,48, thereby producing thesequence s1,1, s1,2 . . . s1,40. An advantage of this is that only asmall amount of matching is required in the system currently in use.

This puncturing pattern can, like other rate matching patterns, beshifted by, for example, an offset 0←k<6. As such, bits r_(1+k),r_(7+k), r_(13+k), r_(19+k), r_(25+k), r_(31+k), r_(37+k), r_(43+k) arepunctured in the case of the 1999 standard (Release 99).

b) The puncturing pattern optimized for the load data of Part 1 of theHS-SCCH “Pattern 1” [1] is used as the puncturing pattern:

Bits r1,1, r1,2, r1,4, r1,8, r1,42, r1,45, r1,47, r1,48 of the sequencer1,1, r1,2, . . . , r1,48 are punctured, thereby producing the sequences1,1, s1,2 . . . s1,40. This variant is advantageous as it optimallycodes the HS-SCCH data and, furthermore, because the sequences formasking the data in the code space are distanced further from eachother, which is to say have a larger what is termed “Hamming distance”,than in the case of puncturing according to the Release 99 puncturingalgorithm.

The term “Hamming distance” is understood to be the number of bits bywhich two equally long codewords differ. This is used for errordetection by comparing received data units with valid characters. Anycorrection required is performed applying the probability principle.

c) A new puncturing pattern which simultaneously optimizes the codingcharacteristics of the data of Part 1 of the HS-SCCH and the detectionpossibilities of masking with the UE ID, can be achieved throughoptimization whereby the secondary conditions are pre-defined by thedata structure in the identification data branch and in the load databranch.Simplified Decoding on the Recipient's Side

As already explained, the proposed simplification of rate matchingoffers a major advantage particularly on the recipient's side, thus in amobile station, for example, owing to less complex decoding.

Differences in decoding as performed at present and as can be performedaccording to the present invention are explained below.

FIG. 5 shows an exemplary implementation in the receiving device asrequired by the present specification (Release 99). The transferred dataTD is received via the air interface AI. Such transferred data TD isdemodulated in the demodulator Demod. After being demodulated, such datais, on the one hand, routed directly to a bit error counter, and on theother hand, linked to the masking data via, for example, an XOR linkingor multiplication operation. Such masking data is generated in themobile station from the mobile station's identification number UE ID,which is coded then subjected to rate matching (RM2). Linking to thedemodulated, transferred data TD takes places immediately thereafter.Rate matching RM2 of the masking data is necessary in order to match thebit lengths of the masking data to the bit length of the received dataTD.

Rate matching RM1 ⁻¹ is rescinded for the linked signal prior todecoding Dec. Such data is decoded and, to check whether the informationwas intended for the respectively receiving mobile station, is codedagain and subjected to further rate matching RM1 before being linked tothe masking data again. The result of this relinking operation likewiseflows into the bit error counter. Error detection is based here on aprocessing of 40 bits, which is to say as many bits as are transmittedover the air interface AI for each HS-SCCH subframe consisting of threetime slots.

FIG. 6 shows two exemplary implementations which can be used with ratematching performed according to the present invention.

In the top illustration (DEC_40), bit error detection in the bit errorcounter is likewise based on 40 bits. As the same rate matching patternis used in the transmitter for identification data ID and load data LD,rate matching is first performed immediately ahead of the bit errorcounter jointly with the transferred data TD received over the airinterface. In this way, there is a saving in one rate matching operationcompared to the prior art; namely, as can be seen in FIG. 5, ratematching of the masking data prior to linking with the received data.

Specifically, the following steps are shown in the top example in FIG.6:

The transferred data TD is received over the air interface AI. Such datais split up after a demodulation operation Demod and flows on the onehand in a first branch directly into a bit error counter. Rate matchingRM⁻¹ is rescinded or cancelled in the other branch, followed by linkingto the masking data generated by coding the mobile stationidentification number. In contrast to the implementation shown in FIG.5, no rate matching of the masking data is necessary as rate matching ofthe transferred data was already rescinded prior to linking. The linkeddata undergoes decoding in a decoding operation Dec. On the one hand,the required data is then available; on the other hand, such data issubjected to coding in a further coding operation and linked to themasking data again. This is done for the purpose of error detection inthe bit error counter into which the data flows after the relinkingoperation and a rate matching operation RM. To summarize, it means asaving in one rate matching operation is achieved compared to theimplementation shown in FIG. 5. This is made possible by the use of acommon rate matching pattern for load data LD and masking data ID in thetransmitter. If different rate matching patterns were used, common ratematching in the rate matching unit RM in FIG. 6 ahead of the bit errorcounter would not lead, for instance, to the original signal.

Even clearer improvements, such as the saving of two rate matchingoperations, are achieved in the implementation shown in the lowerillustration in FIG. 6.

In the lower illustration (DEC_48), bit error detection is based on 48bits. In this case, it is only necessary to rescind rate matching.Further rate matching is not required.

Specifically, the following steps are performed in the lowerillustration in FIG. 6: The transferred data TD is received over the airinterface AI. Rate matching RM⁻¹ is then cancelled, an operation whichis necessary because, on the one hand, the data is routed in a firstbranch directly to the bit error counter in which bit error detectiontakes place based on 48 bits. On the other hand, the data is linked in asecond branch to the masking data generated in the mobile station fromthe mobile station identification number UE ID.

The required data is then available after linking and immediatelyensuing decoding Dec. Analogously to the top example, for ensuing errordetection the data is again subjected to coding Cod, then linked to themasking data. In contrast to the top example shown in FIG. 6, ratematching after linking is not necessary as there are 48 bits on thebasis of which error detection is also performed. No rate matching istherefore required in this implementation.

Further Possible Applications

The joint use of rate matching patterns has been explained, inparticular, for the HS-SCCH, but it is not restricted to this. Load datamasking is also used for other control channels, as a consequence ofwhich the present invention can be used. There are further applicationsbasically for any channels in which different data streams are linked toeach other for transmission and rate matching is required.

Although the present invention has been described with reference tospecific embodiments, those of skill in the art will recognize thatchanges may be made thereto without departing from the spirit and scopeof the present invention as set forth by the hereafter appended claims.

Sources:

-   [1] R1-02-0605, “Coding and Rate Matching for HS-SCCH”, TSG RAN WGI    Meeting #25, Paris, 09-12.04.2002.

1. A method for transmitting data with a defined number of bits via aphysical channel in a communications system, the physical channel beingused by at least one first communication device and one secondcommunication device, the method comprising: providing that the data tobe transmitted is composed of load data and identification data foridentifying the second communication device; separately coding the loaddata and the identification data from each other using convultionalcoding, wherein a same number of bits is produced after the codingoperation for the load data and the identification data; linking thecoded load data and the coded identification data with each other via anXOR linking operation; and matching a data rate to the number of bitsdefined for the physical channel using a rate matching pattern selectedfrom the group consisting of a rate matching pattern used immediatelybefore the XOR linking operation and a rate matching pattern usedimmediately after the XOR linking operation, the rate matching patterndefining which bits in a data stream have at least one characteristicselected from the group consisting of being punctured and beingrepeated, wherein the rate matching pattern for the load data and theidentification data is identical.
 2. A method for transmitting data asclaimed in claim 1, wherein the coding operation supplies a bit sequenceof bits 1 to n in a defined time window by which the rate is defined,and rate matching is performed via a rate matching pattern by whichindividual bits in the bit sequence are punctured.
 3. A method fortransmitting data as claimed in claim 1, wherein the physical channel isa High Speed Shared Control Channel.
 4. A method for transmitting dataas claimed in claim 1, wherein the identification data is anidentification number of a communication device.
 5. A method fortransmitting data as claimed in claim 2, wherein the rate matchingoccurs using a rate matching pattern by which bits at positions 1, 2, 4,8, 42, 45, 47 and 48 are punctured in a bit sequence consisting of n=48bits.
 6. A method for transmitting data as claimed in claim 5, wherein aposition of the bits being punctured is shifted by a whole number k,where 0<k≦5.
 7. A method for transmitting data as claimed in claim 1,wherein linking is bit-by-bit linking.